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Date: Thu, 24 Mar 2016 20:16:58 +0100
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To: Sara Golemon <pollita@php.net>
Cc: "Colin O'Dell" <colinodell@gmail.com>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a114e52605a7872052ed04a5e
Subject: Re: [PHP-DEV] Add spaceship assignment operator
From: nikita.ppv@gmail.com (Nikita Popov)

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On Thu, Mar 24, 2016 at 8:05 PM, Sara Golemon <pollita@php.net> wrote:

> On Thu, Mar 24, 2016 at 11:50 AM, Colin O'Dell <colinodell@gmail.com>
> wrote:
> > Would your proposal also allow !==== to work?
> >
> I think you means !===, which is "not-identical assignment" (!== =)
>
> !==== is just *CRAZY TALK*
>

We shouldn't dismiss such things out of hand, Sara. Consider the following
argument:

There is a binary !== operator. The compound assignment version of it is
!===. But that again is a binary operator! So there should be a !====
compound assignment operator as well. By induction over the natural numbers
it follows that !== followed by an arbitrary number of =s should be a valid
compound assignment operator.

However, when considering the expansion, we see:

    $a !==== $b;
    // same as
    $a = $a !=== $b;
    // same as
    $a = $a = $a !== $b;

It is now evident that $a !==== $b (or any additional number of =s) has the
same meaning as $a !=== $b. A difference could only arise if the left-hand
side is an object implementing __set or ArrayAccess, in which case !====
would cause an additional call to __set / offsetSet.

Given that !==== and !=== would be, apart from the edge-case of overloaded
objects, identical, I must concur with your original judgement that only
supporting !=== is sufficient.

Thanks,
Nikita

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